Four English shepherds and one German shepherd.
The ES are absolutely crucial to having free-range poultry. I could not do it without them. They patrol day and night, chase off hawks (also crows, balloonists, low-flying aircraft) and kill possums and raccoons. I've had absolutely minimal predator loss -- one guinea to an owl, two turkeys that snuck off to nest to a raccoon that the dogs got the next night. And I free-range a lot of birds.
This is not an accident -- it is their genetics and careful training. They've been bred for centuries for small farmstead living, and I was systematic about introducing them to poultry so that they understand the concept of "ours" and protect the birds.
When I had a stranger-mean rooster, my youngest grump was charged with security detail, and accompanied visitors (especially kids) to keep Henery in line. She never harmed a feather on him, just made him think he was about to die.
None of the ES were raised with poultry. The three who were with us when we bought the farm and subsequently got our first chicks were eight, five, and just under one year old. Our youngest came to us at ten months as a foster for National English Shepherd Rescue; he'd been raised in a kennel from the age of four weeks, as criminal evidence in a massive cruelty case, and had no knowledge of the world. He's now just as diligent as the others. I've also had seven other English shepherd fosters in the two years we've been here, and all have been trainable to run free-range with the birds. The last one required the most serious corrections, but even she got it, and is now on another farm with poultry.
My German shepherd is not protective of the birds, but her prey drive is so laser-focused on balls and sticks and retrieving that it's as if the birds don't exist. My dumb guineas used to fly into the kennel run where we'd leave her when we went out, and then run around screaming inside for hours, and she didn't even notice they were there. This is not going to be typical mileage for any dog, much less a working-bred GSD. She's "special."